Article
- The EMBO Journal (2007) 26, 1984 - 1994
- doi:10.1038/sj.emboj.7601643
Published online: 15 March 2007
Subject Categories:
Structural framework for DNA translocation via the viral portal protein
Andrey A Lebedev1, Margret H Krause2, Anabela L Isidro3,4, Alexei A Vagin1, Elena V Orlova5, Joanne Turner1, Eleanor J Dodson1, Paulo Tavares3 and Alfred A Antson1
- York Structural Biology Laboratory, Department of Chemistry, University of York, York, UK
- Max-Planck Institut für Molekulare Genetik, Berlin, Germany
- Unité de Virologie Moléculaire et Structurale, UMR CNRS 2472, UMR INRA 1157 and IFR 115, Gif-sur-Yvette, France
- Instituto de Tecnologia Química e Biológica, Oeiras, Portugal
- Department of Crystallography, Birkbeck College, University of London, London, UK
Correspondence to:
Alfred A Antson, York Structural Biology Laboratory, Department of Chemistry, University of York, York Y010 5YW, UK. Tel.: +44 1904 328255; Fax: +44 1904 328266; E-mail: fred@ysbl.york.ac.uk
Received 17 November 2006; Accepted 13 February 2007
Abstract
Tailed bacteriophages and herpesviruses load their capsids with DNA through a tunnel formed by the portal protein assembly. Here we describe the X-ray structure of the bacteriophage SPP1 portal protein in its isolated 13-subunit form and the pseudoatomic structure of a 12-subunit assembly. The first defines the DNA-interacting segments (tunnel loops) that pack tightly against each other forming the most constricted part of the tunnel; the second shows that the functional dodecameric state must induce variability in the loop positions. Structural observations together with geometrical constraints dictate that in the portal–DNA complex, the loops form an undulating belt that fits and tightly embraces the helical DNA, suggesting that DNA translocation is accompanied by a 'mexican wave' of positional and conformational changes propagating sequentially along this belt.
Keywords:
- bacteriophage SPP1,
- DNA translocation,
- molecular motor,
- viral portal protein,
- X-ray crystallography
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